This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-333370, filed Nov. 24, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to an X-ray computed tomography apparatus having an interlock function of monitoring the operating state of an X-ray tube device and stopping all operations pertaining to scan, including the stop of X-ray emission, when something is wrong about the X-ray tube device.
Helical scan is a scan scheme of continuously and quickly acquiring projection data of a subject in a wide range by continuously rotating an X-ray tube and continuously moving a top plate.
Almost all X-ray computed tomography apparatuses have a function of monitoring an X-ray tube to assure the safety of a subject. The state of the X-ray tube is monitored from various viewpoints using various items such as a tube voltage, tube current, filament current, tube temperature, and cool pump operating status. If any one of the plurality of items exhibits an error value, all operations pertaining to projection data acquisition operation (scanning) are forcibly stopped. More specifically, tube voltage impression, filament current supply, cool pump driving, rotation of a ring on which the X-ray tube and detector are mounted, movement of the top plate of a bed are stopped. This function is called an interlock function.
When scan is stopped by this interlock function, an operator tries to find a cause of the stop of scan and performs a job to remove the cause, as needed. In some case, scan must be restarted from the beginning. In radiographic examination, for example, a change in CT value over time is one of the most important pieces of information. When scan is interrupted by the interlock function, the radiographic effect mostly disappears before the restart of radiographic examination. A contrast medium must be injected again to restart scan from the beginning. In helical scan described above, as the position of the subject often changes while scan is stopped, scan must be restarted from the beginning.
It is an object of the present invention to reduce the frequency of the restart of scan in an X-ray computed tomography apparatus having an interlock function.
An X-ray computed tomography apparatus comprises an X-ray tube configured to emit an X-ray, an X-ray detector configured to detect an X-ray passing through a subject in order to acquire projection data, a processor configured to reconstruct tomographic image data on the basis of the projection data, and an interlock unit configured to monitor generation of an arc in the X-ray tube. When an arc in the X-ray tube is detected, the interlock unit stop X-ray emission from the X-ray tube. When a predetermined period of time elapse from the stop of X-ray emission, the interlock unit restarts X-ray emission from the X-ray tube.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter